The overall objective of the project is to define the functioning of RNA polymerase II. We propose to investigate structure - function relationships within this enzyme by characterizing its putative subunits with respect to their origin and possible function in RNA biosynthesis. The possible proteolytic origin of the low molecular weight subunits will be investigated by examining their peptide fingerprints and comparing them with fingerprints derived from the high molecular weight subunits. Subunits will be isolated using preparative SDS gel and urea electrophoresis. Purified subunits will be used to produce subunit specific antisera for use as probes to investigate subunit function. Also, subunit function will be investigated using subunit depleted enzyme derivatives.